The invention resides in an endoscopically useable surgical instrument for the coagulation of tissue by high frequency application and for the severing of coagulated tissue areas.
Such an instrument is disclosed in German patent P44 21 822 C1. The instrument shown therein has a stationary and a movable jaw with two ranges of movement. The contact surfaces of the two jaws move apart during opening of the jaws first in a parallel fashion. Subsequently, the movable jaw can be pivoted about a pivot axis up to its maximum opening position. With one hand operating the handle, the coagulation apparatus with integrated cutting structure can perform first the coagulation and subsequently, the cutting process by way of a lever mechanism.
It is however a disadvantage of this design that the movable jaw is supported and guided in an unstable manner because of the initial parallel opening movement followed by the pivoting movement: When the clamping forces become large, the movable jaw is canted, whereby the force grasping the tissue is reduced. The subsequent cutting step is performed by an axi ally movable cutting blade, which pushes the tissue to be cut forwardly out of the blade when the cutting resistance becomes excessive or the clamping force is too small.
The printed publication EP 0 572 131 A1 discloses a pair of surgical scissors with a bipolar coagulation arrangement including a stationary and a pivotable cutting blade which is operable by a handle by way of an operating rod. This instrument is also designed for minimally invasive surgery.
With the bipolar surgical scissors, the coagulation and severing of the tissue is performed by the cutting edges of the scissors. In this case, however, it cannot be made sure whether the severed tissue is fully coagulated so that bleeding may well occur during cutting.
It is the object of the present invention to provide a bipolar HF coagulation apparatus with an integrated cutting structure and a handle portion for the operation of the apparatus with one hand whereby the cutting performance is improved and which can be used in minimally invasive surgery.
In an endoscopic surgical instrument for the coagulation, by high frequency energy, and for the severing of coagulated tissue areas, a coagulation pliers and a scissors structure are provided, which are mounted on the distal end of an instrument and which are operated by a handle with operating levers in such a way that, upon actuation of the handle, first the pliers is closed for grasping the tissue while the scissors are closed in a delayed fashion. After coagulation of the tissue engaged by the pliers, actuation of a second lever at the handle end of the instrument fully closes the scissors structure for cutting the tissue in the coagulation area.
The pivot movement of the lever is transmitted to inner tubes of the tubular instrument as longitudinal movement. The longitudinal movement is then converted to pivot movement of the pliers and scissors by way of cross-levers.
The sub-claims define various advantageous embodiments of the invention.
It is essential that, during the closing movement, the scissors movement follow the movement of the coagulation pliers with a predetermined delay. This movement is controlled by the lever arm ratios of the cross levers. The cutting step to be performed after coagulation is completed by a second cross-lever. The invention will be described in greater detail on the basis of the accompanying drawings.